This weekend the battery in my 1999 BMW M3 finally gave out. I bought the car in late 2003, so I know it was at least nine years old and probably was original equipment.
The fact it lasted so long is testament to BMW quality a couple of car generations ago. When my car was new BMW batteries were made by a company called Varta, which made U-boat batteries during WWII. Unfortunately the company was bought by battery giant Johnson Controls in 2002. As a result BMW batteries are no longer any better than aftermarket, just more expensive.
I’ll probably never have another battery as long lasting, so I held off replacing. The two leading candidates for replacement were the Duralast 49-DL and the Interstate MTP-91. I went with the Interstate since my local shop Hollin Hall Automotive carried it and I could pick up right away.
I’m glad I can change the batteries in my cars. Newer BMWs have highly sophisticated electronics that require a trip to the dealer for a reset of the onboard computer when replacing. None of that inconvenient and expensive complexity on the E36.
The process was very easy. Two important things to remember are the vent hose extension and the battery code saver. Since the battery is enclosed in the trunk, there is a hose that vents gases out of the bottom of the car.
If the replacement battery has the vent hole in a different location than stock (like the MTP-91), you need an extension to reach the existing hose. Also, E36s lose all setting and memory, including radio function, when the battery is disconnected. This can be prevented by using an inexpensive plug in the cigarette lighter connected to a 9 volt battery.
I won’t get a decade out of the MTP-91, but I’m set for a few years and happy to be able to DIY it.
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